1 Scope …………………………..2 References…………………………..3 General …………………………..4 Definitions …………………………..5 Application Areas …………………………..6 Fire Service Valve Design 7 Fire Shield Considerations8 Fire-shield Sources …………………………..9 Revision History …………………………..
1 Scope
1.1 This standard establishes criteria and guidelines for specification and protection of
instruments that are deemed critical to the safe and orderly shutdown of a process
plant, in the event of a fire or other serious incident.
1.2 Control valves covered by this standard are not limited by type of design; i.e., globe,
butterfly, ball, plug, pinch, gate, diaphragm, etc, any valve may be specified and/or
protected for fire service.
1.3 This standard will allow for fire exposure for periods of thirty minutes and permit
control of fluid flow, unless the valve is specified to fail to a predetermined position
and remain at that position. Some insulating flame shield systems may be capable of
providing protection for longer periods, but essentially all fire-resistance capability
tests are based upon thirty minutes. The philosophy for this time frame is that
damage to piping and structural support steel is the overwhelming consideration for
longer fire exposure. It is expected that the fire will be brought under control and/or
the plant safely shut down during a thirty-minute period or the situation may evolve to
a fall back and hold strategy. In no way does this fire protection reduce the need to
consider the “fail safe” specifications for control valves. One of the purposes of “fire
safeing” of instruments and valves is to retain control of the device and maintain
information flow for a reasonable time after the fire has started. The fire safe
considerations in this standard are in addition to the usual fail safe considerations.
2 References
SABIC Engineering Standards (SES)
F02-E01 Fire Protection Systems
American Petroleum Industry (API)
API STD 607 Fire Test for Quarter-turn Valves and Valves Equipped with Nonmetallic Seats
3 General
3.1 There is no USA national consensus standard, such as ANSI, for fire-service valves.
Those standards that exist and that may be referenced by valve manufacturers have
been developed by various groups such as industry associations (API), insurers (FM),
countries or user companies. All of these standards may differ markedly and in many
respects do not actually reflect all real-world safety considerations. Their approach is
to allow a qualification testing of different valves, based upon a “Standard Test Fire”
and procedure.
3.2 The most common referenced standards by manufacturers are the API (American
Petroleum Institute) Publications. It is API STD 607. Other standards are FM–6033
(Factory Mutual) and BS–6755–Part 2 (British). The API standard and the British
standard are essentially identical, except for minor differences in wording, and are the
primary accepted international documents. All of these standards address only the
valve and do not consider the power operator or pipe closure flanges. The API is
addressing the question of the power operator. The fire test qualification for SABIC
valves shall be either API STD 607 or BSI 6755–Part 2 for international work, or a
new standard.
3.3 Manufacturer references to one or more of the above standards, as a sole
qualification for a valve design, should not be construed as satisfactory for SABIC
service or safety considerations. Where a valve is adequately protected from fire
exposure, it is not necessary to use a valve design qualified by these standards. If a
valve is not, or cannot be adequately protected, then a fire-service qualified valve is
required if it is deemed critical to plant shutdown. Such requirements are usually the
result of a complete and thorough hazards analysis of the overall process system.
4
Definitions
4.1 A fire-service valve is any valve which meets certain criteria and specifications of
performance during and after being exposed to a fire. It can be a manually or poweroperated
valve.
4.2 The performance specifications generally define the permissible leakage through the
valve seat and external from the valve during and after a fire. Valve operability with
fire exposure is also a factor.
4.3 Fire-service valves usually have special design features in the seating, packing and
gaskets, but this is not always the case. It is possible for any standard design valve to
be used in fire service provided proper and adequate protection is given. As an
example, in the case of control valves, where PTFE is the preferred packing, flexible
graphite packing can be considered inherently fire resistant.
5 Application Areas
5.1
It is not possible to state specifically where fire-service valves should be installed.
This requires a hazard analysis. Such an analysis coupled with a “what if” scenario
will usually determine locations and situations where a fire-service valve installation
should be considered
5.2 Some areas that should be considered are:
a. Piping to and from storage areas holding flammables
b.
Feed lines to a reactor or process unit
c. Emergency bottle-up and venting valves
d. Barge or tanker loading docks handling flammables
e.
Long transport piping
f.
Tank truck and tank car loading and unloading areas Each case must be
individually analyzed based upon the type of fluid, pressure, temperature,
physical properties, location, vulnerability factors, fire consequences, etc.
6
Fire Service Valve Design
6.1 Valve gaskets should be limited to metallic materials, graphite, or suitable fireresistant
substitutes if available. If PTFE base gaskets are a requirement due to
corrosion or other conditions, then a fire-shield or other protection of the valve is
mandatory.
6.2
In general, PTFE packing is the only suitable material for sliding stem valves for
control services. Graphite packing is subject to some problems in these services, but
may be required where the service conditions are beyond PTFE. Asbestos packing in
any form is being phased out completely by government regulation and shall not be
specified.
6.3 For rotary stem valves, graphite packing is adequate but PTFE is still preferable.
Asbestos should not be considered.
6.4 A fire-shield or other protection is mandatory for fire-service valves with PTFE
packing and/or gaskets.
6.5 Flangeless valve designs, which require long and exposed pipe closure bolting are
not acceptable for fire service unless fully protected. Such exposed bolting during a
fire will likely result in catastrophic failure of the pipe closure joints. Examples are
certain rotary plug designs, wafer butterflies, flangeless globe and ball valves. Even
with protection, strong consideration should be given to using full flanged valves,
including single flange or lug pattern butterfly valves.
6.6 Valves with small body closure joints are generally preferable to those with large body
joints. No body closure joints is best, but not always available in every type of valve
design.
6.7 All things considered, it is preferable to use a metal-seated valve.
Where soft-seated valves are necessary, it is better to choose designs which
incorporate combined soft and metal seats which operate simultaneously on valve
closing. Less desirable are designs which have a secondary metal seat which comes
into play only when the primary soft-seat is completely destroyed in a fire. This is
because there is no guarantee in a fire situation that the soft-seat will be completely
destroyed to allow the metal backup seat to function. This can result in a considerable
through-leakage path.
6.8 Cast iron, ductile iron, brass, and bronze are not acceptable as body and bonnet
materials. Only carbon steel, alloy steel, stainless steel, or other suitable alloys are
acceptable for use in fire-service valves. The most common valve designs used for
fire service are ball, high-performance butterfly, and globe. Gate and plug valves are
the least desirable, but can be used with proper protection. Careful consideration
must be given to all aspects of a particular valve design, regardless of any vendor
“certification.”
6.9
In general, as a valve increases in size and/or pressure rating, it becomes less and
less vulnerable to a fire from the standpoint of soft-seat damage or destruction. This
is because the metal mass is such a large heat sink that it is almost impossible to
generate enough heat flux to bring the valve up to a high temperature.
7
Fire Shield Considerations
7.1 Presently available fire shields are designed for the normal flame temperatures (2000
to 2500°F) for all common flammable materials with a minimum exposure of 30
minutes. See also 7.1.
7.2
Rigid fire shields consist of insulating panels in the form of a box or metal mesh
reinforced molded insulating shell. Flexible type usually consists of a blanket of
insulating fibers of glass or mineral wool with a waterproof woven Fiberglas cover.
7.3 For new installations, provisions for needed fire shields should be determined during
the design phase to allow for any space considerations and routing of signal and
power to a single penetration. For retrofit, it is preferable that the signal and power be
reworked as needed to a single penetration. Where this is not feasible, then multiple
penetrations can be provided at a greater cost.
7.4 Adequate fire protection of all components in a system critical to safe and orderly
shutdown also requires protection. This includes signal and power wiring or tubing to
the valves, key transmitters and sensors, junction boxes, support trays, etc. Careful
consideration of each part of the system and the means of protection by proper
choice of fire shield is vital to the use of the system during critical fire or explosion
incidents
7.5 Fire-shield systems should be regularly inspected and maintained as benefits any
safety device. Maintenance access flaps or panels should not be left open any longer
than required. The efficiency of the protection is dependent upon these rules being
followed.
7.6 Fire proofing of instrumentation and control system shall follow SES-F02-E01.
8
Fire-shield Sources
8.1 There are commercial sources of fire shields available most of which are aimed at a
protection time of approximately 30 minutes to allow orderly plant shutdown. The
majority of these sources provide the rigid type of fire shield intended for protecting
electric type actuators such as Limitorque, Rotork, etc, or the pneumatic types such
as Bettis, Automax, etc. Currently there is only one source of the soft or blanket type
fire shield. There is also one source of a rigid fire-shield system that can actually be
considered fireproof, having passed the UL263/ASTM E 119 two-hour fire test
minimum qualification. This latter system can be furnished in cast panels (for boxes,
curtains, barriers, etc), sprayed and troweled (monolithic) configurations. There is
also a source for fire survey and evaluation services for fire-shield and barrier
installation protection recommendations. In addition, this source can provide an allpneumatic
operator
equivalent
to
the
Limitorque/
Rotork
type.
These best sources for the above are as follows:
Fire Survey & Protection Evaluation Services
Consulting Design Engineering, Inc
7 Cromwell Court
Rancho Mirage, CA 92270
(619) 326-1226
FAX: (619) 322-6325
R. A. Strand
Rigid Fire Shield Box (Fireproof Type)
AEREX International Corporation
P.O. Box 924286
Houston, TX 77292-4286
(713) 688-6666
FAX: (713) 688-5914
R. E. Ginn
Soft/Blanket Fire Shield (30-Minute Exposure)
Darchem-Flame Control Systems, Inc
81 West Bellevue Drive
Pasadena, CA 91105-0247
(818) 449-3222
FAX: (818) 792-1246
F. G. Scholl